Objective To observe the effect of panretinal photocoagulation (PRP) on the expression of cyclooxygenase-2 (COX-2), vascular endothelial cell growth factor (VEGF) in epiretinal membrane of proliferative diabetic retinopathy (PDR). Methods Atotal of 35 patients (35 eyes) with PDR and underwent plana vitrectomy were enrolled in this study. The patients were divided into non-PRP group (19 patients, 19 eyes) and PRP group (16 patients, 16 eyes) depends on if they had received PRP before surgery. The epiretinal membranes stripped during operation were collected for pathological examination. The histopathological features was observed by haematoxylin and eosin stain. The expression of CD34, COX-2 and VEGF, and microvessel density (MVD) were measured by immunohistochemistry method. Results Many new dispersed capillary blood vessels were found in the thick epiretinal membranes of non-PRP group, while scattered small blood vessels were found in the relatively thin epiretinal membranes of PRP group. MVD value was (7.42±1.39) in the non-PRP group and (4.56±1.22) in the PRP group, which was lower than the non-PRP group (t=6.41, P<0.01). The expression of CD34, COX-2 and VEGF in the tissues of epiretinal membrane in PRP group were obviously lower than the non-PRP group (t=6.147, 5.944, 7.445; P<0.01). Conclusion PRP can effectively inhibit the expression of COX-2 and VEGF in epiretinal membrane of PRP patients.